docs: def reduce(self, key, values):
          """Select the image with the minimum distance
  
          Args:
              key: (see mapper)
              values: (see mapper)
  
          Yields:
              A tuple in the form of (key, value)
              key: Image name
              value: Image as jpeg byte data
          """
          
          dist, key, value = min(values, key=lambda x: x[0])
          print('MinDist[%f]' % dist)
          yield key, value